http://www.idownloadblog.com/2017/02/10/how-to-enable-and-use-two-step-verification-on-whatsapp/

How to enable and use two-step verification on WhatsApp

An optional measure designed to help strengthen the security of your account, two-step verification requires that you verify your mobile phone number after installing WhatsApp’s mobile app on a new device with a six-digit code that you created using this feature.

Things to know about two-step verification on WhatsApp

This feature requires you to create a six-digit passcode and provide an optional rescue email address. Upon enabling two-step verification, you’ll need to enter the passcode every time you install WhatsApp on a new device.

Unlike similar two-step verification systems, WhatsApp doesn’t generate these passcodes for you—each and every user is required to create their custom passcode for two-step verification.

As a fallback mechanism, you can provide a rescue email address where WhatsApp will send you a link to disable two-step verification if you forget the passcode.

Think twice before skipping this step: if you enable two-step verification without providing an email address, and you forget your passcode, WhatsApp will lock you out of your account.

If you forget the passcode but did not provide a rescue email address, you won’t be allowed to reverify your mobile phone number within seven days of last using WhatsApp.

After seven days, your number will be permitted to reverify on WhatsApp without the passcode, but all pending messages upon reverifying will be deleted.

Lastly, and most importantly, if your mobile phone number is reverified on WhatsApp after 30 days of last using the service, and without the passcode, your account will be deleted and a new one will be created upon successfully reverifying.